• Journal of Welding and Joining
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• 제32권4호
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• pp.63-68
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• 2014

This paper has an aim to study the effect of PWHT and its conditions(peak temperature and holding time) on the tensile properties and impact toughness of FCAW weld metal in relation to microstructure. Impact toughness was evaluated to apply the cargo tank of liquified gas carriers under the various PWHT condition of each class societies. On the basis of these study, it was found that PWHT conditions within all class societies affect charpy absorbed energy of weld metal little or no, all PWHT weld metals kept similar level of charpy absorbed energy as as-weld weld metal down-to $-60^{\circ}C$ and finally indicated lower energy value than that of as-weld weld metal at $-75^{\circ}C$. It is because the precipitation of 2nd phase was controlled from welding consumable and the grain size was grown by PWHT.

• Journal of the Korean Wood Science and Technology
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• 제39권4호
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• pp.311-317
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• 2011

라디에타 소나무(Pinus radiata D.Don)를 압체온도 $180^{\circ}C$, 압체시간 60분 조건으로 열압밀화 목재를 제작하여 압축세트량에 따른 종압축강도, 휨강도, 경도, 못뽑기저항을 조사하였다. 압축세트량 60%인 열압밀화 목재의 비중은 1.01로 나타났으며, 대조군의 비중 0.48에 비해 현저히 증가한 값을 나타내었다. 압축세트량의 증가와 함께 모든 역학적 특성도 향상되었다. 그리고 라디에타 소나무의 최대 압축세트량은 약 65%로 확인되었으며, 이는 비중 0.48인 라디에타 소나무의 공극율 68%와 거의 일치하는 결과이다.

• 동아시아식생활학회지
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• 제23권6호
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• pp.778-788
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• 2013

The objective of this study was to investigate the effects and availability of arrowroot powder in making white bread. The characteristics of pasting, farinogram and alveogram of the dough containing arrowroot powder were analyzed. Further, the physicochemical properties of white bread were analyzed by different mixing ratios (0, 3, 5 and 7%) of arrowroot powder during storage periods. When 7% of arrowroot powder was added, the initial pasting temperature of the dough by using a RVA (rapid visco analyzer) was significantly increased. Peak viscosity, holding strength, break down, final viscosity and set back were decreased by increasing added arrowroot powder. With the increasing amounts of arrowroot powder, the values of farinogram and alveogram parameter for the dough showed a tendency to decrement. The texture profile analysis of the white bread revealed that hardness, springiness, cohesiveness and gumminess were increased by adding arrowroot powder and further, the storage time was longer. By increasing the amount of added arrowroot powder, the L value of the white bread was decreased, whereas the a, b value were increased. In the sensory evaluation, the white bread of the control and that of the added 3% arrowroot powder showed the highest preference in total score.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.43.2-43.2
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• 2010

In this study, metallurgical grade (MG) silicon with 99% purity produced by arc furnace process was systematically investigated for slag refining. The most problematic impurities to remove from MG silicon are boron (B) and phosphorus (P). To remove B and P from MG-silicon, we used synthetic slag in the molten state. MG-silicon with synthetic slag of CaO, $SiO_2$, and $CaF_2$ was melted using by high-frequency induction furnace with electrical output of 50kW. Specimens prepared by various refining process conditions(holding time, mixture ratio) were inspected by combined analysis of ICP-MS and XRF. With this approach, B has been reduced to <5ppm, P to <1ppm and other impurities to 0.1~0.2% except for Calcium. Calcium has been increased from 17ppm to 1500ppm. Problem of calcium contamination will be resolved by additional refining processes.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1400-1413
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• 1997

Semi-solid forging(SSF) process of A356 aluminium alloy has been studied to assess the effect of process variables on the component integrity. Semi-solid material(SSM) was fabricated by mechanical and electro-magnetic stirring process. The fabricated SSM by using mechanical stirring process has been carried out on cooling rate of 0.022.deg. C/sec 0.0094.deg. C/sec and stirring speed n=600, 1000 rpm, respectively. The fabricated SSM by using electro-magnetic stirring process is supplied by Pechiney. The holding time and temperature in the semi-solid state before forging also affects the globular microstructure of alloy. Therefore, the influence of these two parameters is discussed in terms of the microstructure of alloy. The SSF process has been conducted with three different die temperatures($T_{die}$=250.deg. C, 300.deg. C, 350.deg. C) and two kinds of gate types(straight gate and orifice gate). This paper is to investigate the influence of gate shapes of die on filling phenomena in SSF process more deeply. The mechanical properties of forged components were also investigated for variation of process conditions such as die temperature, gate shape and SSM.

• 대한기계학회논문집A
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• 제21권9호
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• pp.1452-1461
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• 1997

The hot press apparatus to obtain the solidified rocks with 60mm of diameter against rock waste was developed, and the optimum conditions for solidification were founded out, of which were 300.deg. C of temperature and 1hr of holding time. The solidified rocks reinforced with the fibers (carbon, steel) were made by means of a hydrothermal hot press method. Fracture toughness of those was obtained using the round compact tension(RCT) specimens. Load and displacement behaviours of the solidified rocks reinforced with the fibers were dependent upon the fiber volume fraction and kind of the fibers. Strength and fracture energy of the solidified rocks with steel were much larger than those of the solidified ones with carbon because of the Bridge's effect, multiple cracking and crack branching phenomena.

• 자원리싸이클링
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• 제28권6호
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• pp.87-95
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• 2019

본 연구에서는 인쇄회로기판(PCB) 제조 공정 중 발생한 슬러지 내 구리를 회수하기 위한 건식야금 공정 변수에 대해 조사하였다. 에칭 및 도금 공정에서 발생한 슬러지는 전처리 공정을 통해 수분과 유기물을 제거하였다. 열역학 상평형 계산을 통해 평형상과 슬래그 시스템을 선정하였으며, 유가금속 회수율에 미치는 건식야금 공정 변수에 대하여 조사하였다.

• 열처리공학회지
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• 제28권3호
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• pp.139-145
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• 2015

Effects of austenitizing, cryogenic treatment and tempering conditions on the phase change, microstructure and Vickers hardness value have been studied in STD11 steel for tool and die. The volume fraction of retained austenite increased with a rise in austenitizing temperature, while the volume fraction of eutectoid $M_7C_3$ carbides decreased. The retained austenite could be reduced by cryogenic treatment i.e., maintaining at $LN_2$ temperature ($-196^{\circ}C$) for 12hrs but a little amount of retained austenite did not transform to martensite further although holding time increased to 24 hrs or more. The microstructure of the quenched and then cryogenictreated specimen showed nano-sized and needle-shaped carbides in matrix due to the decomposition of martensite by tempering, but that of the one without cryogenic treatment still revealed retained austenite by tempering even at $500^{\circ}C$.

• 대한기계학회논문집
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• 제19권4호
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• pp.1023-1032
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• 1995

The multiple cooperating robot system plays an important role in the research of modern manufacturing system as the emphasis of production automation is more on the side of flexibility than before. While the kinematic and dynamic analysis of a single robot is performed as an open-loop chain, the dynamic formulation of robot in a multiple cooperating robot system differs from that of a single robot when the multiple cooperating robots form a closed kinematic chain holding an object simultaneously. The object may be any type from a rigid body to a multi-joint linkage. The mobility of the system depends on the kinematic configuration of the closed kinematic chain formed by robots and object, which also decides the number of independent input parameters. Since the mobility is not the same as the number of robot joints, proper constraint condition is sought. The constraints may be such that : the number of active robot joints is kept the same as mobility, all robot joints are active and have interrelations between each joint forces/torques, two robots have master-slave relation, or so on. The dynamic formulation of system is obtained. The formulation is based on recursive dual-number screw-calculus Newton-Eulerian approach which has been used for single robot analysis. This new scheme is recursive and compact symbolically and may facilitate the consideration of the object in real time.

• 한국세라믹학회지
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• 제46권1호
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• pp.53-57
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• 2009

The h-BN powder was synthesized by amorphous $B_2O_3$ and activated carbon at $1550^{\circ}C$ in nitrogen atmosphere, whose properties were examined according to $MgB_6$ addition. Amount of $MgB_6$ addition was varied in the range of $0{\sim}$10\;wt% of the initial mixture. It was observed that $MgB_6$ addition led to an increase in the amount and the grain size of h-BN and decrease in the amount of $B_4C$ forming. When $MgB_6$ added 5 wt%, the amount and crystallinity of h-BN increased as the holding time at the synthesis temperature was prolonged. It was also confirmed that the regularity of three-dimensional ordering of h-BN increases.